1970: The first "Earth Day" observation was held throughout the world. More than 20 million people took part, making it the largest organized demonstration in history.

1970: The Environmental Protection Agency (EPA) was created by Congress to control water and air pollution.

1973: Members of the American Indian Movement seized the village of Wounded Knee, South Dakota, the site where Sioux Indians had been massacred by the U.S. Cavalry in 1890. Two Indians were killed by police in the 70-day occupation, and the village of Wounded Knee was destroyed by fire.

1973: A global energy crisis emerged, and President Richard Nixon encouraged Americans to conserve. He pointed out that the United States had 6% of the population but consumed nearly 35% of the world's energy.

1989: Brazil, South America's wealthiest country, began to regulate previously uncontrolled land clearances in the Amazon basin after profiting for years on the destruction of the land.

1992: Seven...